Conversation timing trunk circuit



April 15, 1958 E. H. GATzERT 2,831,062

coNvERsATIoN TIMING TRUNK CIRCUIT l mnu-P2 f V-O 30 l T MER I I I l Tl I I I I I I ERNEST H. GATZERT AGT E. H. GATZERT 5 Sheets-Sheet 2 4iso . sHuNT 424 Fig. 4

April 15, 1958 coNvERsATIoN TIMING TRUNK CIRCUIT Filed July 29. 1955 April 15, 1958 E. H. GATzERT 2,831,062

CONVERSATION TIMING TRUNK` CIRCUIT Filed July 29, 1955 3 Sheets-Sheet 3 I f l s I l I l E@ l v H CONVERSATIN TIMNG TRUNK CHRCUT Ernest H. Gatzert, Rochester, N. Y., assigner to General Dynamics Corporation, a corporation Delaware Application July 29, 1955, Serial No. 525,254

4 Claims. (Cl. 179--7.1)

This invention relates to trunk circuits equipped for conversation timing and more particularly to a method for connecting common timing apparatue to any one of a group of individual trunks.

It is the practice to provide connecting apparatus iudividual to each timed trunk circuit for extending a connection from a common timer circuit to control apparatus within each trunk circuit. The control apparatus is eiiective for causing the well known holding means within each trunk circuit to release an established connection set up through the trunk circuit and a train of switches a predetermined time interval after such a conection has been established. It is generally accepted practice to provide apparatus for applying a warning tone to such an established connection that is about to be released by the action of the timer. in such systems, it has been necessary to provide a group of relays associated with `each of the trunk circuits equipped for conversation timing for the sole purpose of extending connections between the common timing apparatus and the individual trunk circuits as well as relays for such purposes as connecting the source of warning tone to the individual established connection.

Accordingly, it is an object of my invention to provide new Iand improved means for extending a connection between a common timer circuit and connection holding apparatus individual to `each one of a group of trunk circuits.

I accomplish this and other objects by providing a telephone system comprising a switch -train for establishing y connections and means such as ia trunk termination for controlling the switch train. Means associated with the connection establishing equipment is operative resposive to the seizure of the switch train for operating means for holding the switch train after a connection has been established. Common to a group of such lholding means is a circuit for periodically producing spaced-apart timing signals. Responsive to the transmission of a supervisory signal, which marks the establishment of a connection and the beginning of a conversation, means comprising a twostep relay having a normal and rst second operated positions is operative to its second position (i. e., through its second step) for maintaining the holding means in operated condition under the control of signals from the timing signal producing means. The timing signal producing means is thereafter operative in response to the operation of the two-step relay through its second step for releasing the relay to its normal position. The timing signal producing means is thereafter operative a predetermined time interval following the operation of the supervisory means for releasing the holding means in order to disable the established connection after the time-out period has elapsed. Another signal transmitted from the timing signal producing means is operative in response to the release of the relay during the time that the holding means is being maintained in operated condition for reoperating the relay to its iirst p osition (i. e., through its iirst step). Means comprising contacts on `the relay ,p 2,8%,062' Patented Apr. l5, i958 which are effective only in response to the operation of the relay through its first step are then effective for connecting a warning tone source to the termination to indicate to the connection that the cutoff is about to occur.

Further objects and advantages of my invetnion will become apparent as the following description proceeds, and the features of novelty which characterize it will `be pointed out with particularity in the claims annexed to and forming a part of this speciiication.

For la better understanding of my invention, reference may be had to the accompanying drawings in which:

Fig. l is a skeletonized representation of apparatus found at the calling end of a trunk circuit;

Fig. 2 shows a representation in block form -of an interrupter circuit;

Figs. 3-5 show a termination for an incoming trunk circuit;

Fig. 5 also shows skeletonized representations of an incoming selector, a connector, and a subscriber line; and

Fig. 6 shows a timing chart representing the output impulses of the timer circuit of Fig. 2.

The apparatus which forms the preferred embodiment of my invention is made to function from a source of power such as a battery. The most positive plate or Iterminal of thisbattery is connected to ground and is hereinafter referred to as ground and in the drawings as (-1-). The most negative, ungrounded terminal or plate of the battery is hereinafter referred to as battery and in the ldrawings as Referring to Fig. l, a call may be originated by seizing an outgoing trunk such as the one comprising conductors T1 and Rl by the well known method of completing a short between the conductors by means such as dial contacts 101. The completion of the short iseiiective for operating calling bridge relay 466i in the incoming trunk termination shown in Figs. 3-5 over the following loop: from ground, through the upper winding of relay ddii, re-

sistor R40, the upper lefthand winding of repeat coil RC40, break contacts 321, conductor T1, break contacts 101 of the dial, conductor Rl, break contacts 323, the lower lefthand winding of repeat coil RCiil, resistor R41, and the lower winding of relay 400 to battery.

The operation of relay fitti? is effective for operating circuit holding means comprising release delay relay 500 `within the trunk termination over the following path: from ground, through break contacts 307 and 315, make contacts 401, and the winding of relay Sti@ to battery. At this time the operation of relay Stitl is effective to close a circuit for the lower biasing winding ofthe well known supervisory relay 320 through make contacts 502 and resistor R32, and for seizing the incoming selector lSt-i. which is of the well known step-by-step type, by closing a loop circuit for selector 1850) comprising conductor T4, 'the upper righthand winding of repeat coil RCMP, the upper winding of supervisory relay 320, resistor Rl, the lower righthand winding of repeat coil RCM), 'break contacts 431, make contacts 591, and conductor R4. Relay 320 is unoperated because the current iiowing through the upper winding from the .succeeding switch train is in such a direction that it causes ux in the magnetic circuit of relay 320 that is opposed to the flux caused by current flowing through the lower biasing winding of the same relay. The contacts Sill are thereafter effective for maintaining the loop' in order to hold the switch train including selector iSd-@t3 and connector Ciiiti. The holding process is described in more detail in the following paragraphs.

Incoming selector iSSltl is next driven to the required level and advanced within that level to seize a connector circuit such as C5233. Connector C500 is then advanced in its primar;7 and secondary directions in order to seize a subscriber line such as A. The process of advancing sciector IS500 and thereafter connector C500 is carried out in the well known manner in response to the repetition of trains of impulses by relay 400 when the latter repeats impulses caused by the opening and closing of dial contacts 103i. impulse repeating contacts 402 in relay 400 drive well known 'pulse correcting means comprising pulse correction 1 and pulse correction 2 relays, 420 and 430 respectively, in the trunk termination. Relays and 430 are thereupon effective in the well known manner in response to the operation of impulses repeating contacts 402 for repeating trains of corrected impulses to the succeeding switch train by opening and closing the previously traced loop comprising conductors T4 and R4 at break contacts 431. Such impulses drive selector 18500 and thereafter connector C500 in a manner well understood by tnose skilled in the telephone art. Because the advance of the switch train does not form a part of the present invention, a detailed description of the, process is not considered to be necessary.

After a connection has been extended to station A, the connection is completed by the answering of the telephone at station A. rhereupon, means such as hookswitch'contact H501 at station A are closed in order to send back a supervisory signal into connector C500 to operate supervisory relay 510. The operation of relay 510 causes a signal to be transmitted from connector C500 to the incoming trunk termination in the form of a reversal in the direction of current flow through the previously described loop comprising conductors T4 and R4 and the upper winding of supervisory relay 320. The reversal is caused by the opening of break contacts 511 and 513 and the closing of make contacts 512 and 514. The reversal of current flowing through the upper winding of relay 320 is effective for altering the magnetic tield of that relay so that the flux created by current flowing in the upper and lower windings is additive and therefore snicient to cause relay 320 to operate.

The operation of relay 320 is effective for reversing the direction of current flow in the trunk conductors T1 and R1 in the well known manner to signal an off-hook condition at station A to the apparatus in Fig. l. The operation of relay 320 is also effective at this time for starting the timing process by transferring the winding of release delay relay 500 from its above described connection which was completed by the operation of they seizure responsive relay 400 to means controlled by the cyclically operating timing impulses generating means shown in the block representation of Fig. 2. The timing process is next described.

The timing impulse generating means may be of the rotary type. Because such apparatus is well known and understood by those skilled in the telephone art, a detailed description of its operation here is not considered to be necessarv to the understanding of the present invention. Referring to Fig. 6, upon the start of the cycle of operations of the timing impulse producing means of Fig. 2, a timing start signal comprising a ground impulse is placed on conductor TF1 and is effective for completing an operating circuit for the two-step timer-connector l relay 310. This circuit is traced as follows: from conductor TPL through break contacts 301, make contacts 326, break contacts 312, and the upper winding of relay 310 to battery. The operation of relay 310 is effective for establishing a holding circuit for relay 310 which is traced as follows: from ground, through make contacts 502, break contacts 303, make contacts 311, and the upper winding of relay 310 to battery. Thus itis seen that relay 310 is held in operated condition from ground supplied through the contacts of release delay relay 500 at time. The operation of relay 310 is also effective for transferring the energizing circuit for release delay re- 1ay500 from the previously traced ground source which included break contacts 315 and 307 to a direct ground source by closing make contacts 316 and opening break contacts 315.

After the timer, shown in Fig. 2, has completed a rst cycle of operations a ground impulse is placed on conductor TF2. The placing of the ground impulse on conductor TPZ is effective for completing an operating circuit for the remainder of the timer connecting means, namely, timer-connector 2 relay 300. The circuit is traced as follows: from conductor TPZ, through now closed make contacts 314, break contacts 306, and the winding of relay 300 to battery. Relay 300 thereupon opcrates and closes the following locking circuit for itself: from ground, through make contacts S03, make contacts 30S, and the winding of relay 300 to battery. The operation of relay 300 is also effective to transferk the upper winding of relay 310 from its previously traced holding circuit which included break contacts 303 to a holding circuit comprising conductor H1. It is to be noted in Fig. 6 that at the time that relay 300 is operated in response to the impulse on conductor TPZ, the timing impulse producing means has placed ground on conductor H1. Owing to the make-before-break nature of contacts 302 and 303, the transfer of the holding circuit for the upper winding of relay 310 is accomplished without interruption so that relay 310 is held operated steadily during the operation of relay 300.

The timing impulse connecting means comprising relays 300 and 310 remain in this condition until the appearance of a rst absence of ground signal on conductor H1 which occurs toward the end of the cycle of operations of the timing impulse producing means. The absence of ground on conductor H1 is of sumcient duration to allow relay 310 to be released. The release of relay 310 is effective for transferring the previously described holding circuit for relay 500 which included operated make contacts 316 on relay 310 to a holding ground supplied as a second signal from timing pulse producing means over conductor H2. The latter circuit is traced as follows: from conductor H2, through make contacts 308,bre'ak contacts 315, make contacts 401, and the Winding of relay 500 to battery. Thus, relay 500 is thereafter maintained in its operated condition so long as the ground is held on conductor H2. it is to be noted in Fig. 6`that at the time that ground is removed from the H1 conductor, ground is present on the H2 conductor and continues t'o be present until the completion of the current as well as the next succeeding cycle of operations of the timing impulse producing means.

Assume that the above described connection from Fig. l through selector 18500 and connector C500 to station A is held for an interval greater than the maximum'timed interval. In the preferred embodiment of my invention such a time interval is measured by three full cycles of operations of the impulse producing means shown in Fig. 2. During the last of these cycles of operations, the above described operation of relay 300 and the release F of relay 310 is effective for completing a circuit comprising break contacts 313 and 304 for extending a connection from conversation warning tone conductor CWT to the upper winding of relay 310 upon the appearance of a third signal comprising a ground impulse on lead CWT during the third (last) of the cycles of operations of the timing impulse producing means. The circuit is traced as follows: from conductor CWT, through make contacts 304, break contacts 313, resistor R30, and the upper winding of relay 310 to battery. Resistor R30 limits the current owing within the upper winding of relays 310 to a point that is sufficient to operate the two step relay through its rst step only. Accordingly, only the preliminary contacts such as 318 on relay 310 are operated at this time. All other contacts remain in their normal, released condition. Accordingly, the operation of relay 300 and the operation of relay 310 through its first step completes a circuit from the tone source comprising generator GR30 which is traced as follows: from ground, through generator. GR30, blocking condenser C30, now 'operated make contacts 309 and 318, break acerbes contacts 317, the lower lefthand winding of repeat coil RCM), and the resistance-capacitance network comprising capacitor C31 and resistors and Rill to ground through the windings of calling bridge relay dll. The application of the potential is sufficient to cause a tone to be heard at stations such as A which are a part of the above described connection and warn the subscriber using the station that the conversation is about to be cut off.

From Fig. 6 it is seen that at the end of the third cycle of operations of the timing impulse producing means (following the removal of the ground impulse from conductor CWT and the resulting re-release of relay 310), ground is removed from conductor H2. The absence of ground signal on conductor H2 opens the last traced holding circuit for release delay relay 500. Relay 590 thereupon releases.

The release of the holding means comprising relay 501i is effective for opening the seizing and holding loop circuit at make contacts 501. The switches in the connection, such as 18500 and C501), are thereupon restored in the well known manner to their normal conditions to break the previously traced connection established through the switch train a predetermined time interval following the transmission of off-hook supervision from station A to the trunk termination.

In the event that a call is routed through the switching means comprising incoming selector 1850i) to a destination, such as an outgoing trunk OGT, it may be desirable to cancel the above described operation of the conversation timing facilities. Such trunks are usually located within a particular level to which the selector has access. In order to provide a signal for causing the cancellation of the timing facilities, well known level marking means within selector 18595 comprising a wiper, such as S51, is advanced one step over a bank of conductors for each primary step taken by the switch wiper, shown collectively as S50. A more detailed description of such level marking means may be found in Patent 2,669,606, issued February 16, 1954, to Frank Kessler et al. and assigned to the present assignee of record. In the preferred embodiment of my invention, such outgoing trunks are shown connected in the sixth level. Thus, when wiper S51 is advanced to the sixth successive contact, a signal is transmitted over the following circuit for operating timer-connector relay 31d: from ground, through wiper S51, conductor LM, and the lower winding of relay 3l() to battery. Relay 310 thereupon operates and remains operated throughout the duration of the call. The subsequent operation of relay 313i) and the transfer of the upper winding from the holding ground to the conductor H in the previously described manner is now ineffective to bring about the release of relay 310 in the previously described manner. Under these conditions relay 50d is held operated under the control of make contacts 401 on calling bridge relay titl from ground supplied through make contacts 3io. The timing impulse producing means is therefore not elective for causing the release of the holding means comprising relay 59d and calls extended through the sixth level of selector 1550i).

While I have shown and described a specific embodiment of my invention, other modifications will readily occur to those skilled in the art. I do not, therefore, desire my invention to be limited to the specific arrangement shown and described, and I intend in the appended claims to cover all modifications within the spirit and scope of my invention.

What is claimed is:

l. In a telephone system, means comprising a switch train for establishing a connection, means for seizing and thereafter controlling the advance of said train, means for holding said train, means operative in response to the operation of said seizing means for operating said holding means, means for periodically producing timing signals,

CFI

means for transmitting supervisory signals over a connection established over said switch train, means for repeating supervisory signals, means comprising a relay having a normal position and first and second `operated positions operative to its second position in response to the operation of said supervisory means for thereafter maintaining said holding means operated under the control of said timing signal producing means, said timing signal producing means being operative for releasing said relay to its normal position and thereafter operative in response to the elease of said relay a predetermined interval of time following the operation of said supervisory means for releasing said holding means, means utilizing another signal from said timing signal producing means and e'ective in response to the release of said relay prior to the release of said holding means for operating said relay to its first position, a tone source, and means operative in response to the operation of said relay to its first position for connecting said tone source to a connection established over said switch train.

2. The system set forth in claim l and having in addition means operative in response to the establishment of a connection through said switch train over a particular route for operating said relay to its second position, whereby the release of said holding means by said timing means is prevented.

3. In a telephone system, means comprising a switch train for establishing a connection, a trunk termination circuit for seizing and thereafter controlling the advance of said switch in said train, means for holding said switch train, a circuit for operating said holding means, means operative in response to the seizure of said termination for completing said circuit over a tirst path, means for periodically producing a plurality ot timing signals, means for transmitting supervisory signals over a connection established over said switch train, means for repeating supervisory signals, means comprising a relay having a normal position and lirst and second operated positions operative to its second position in response to the operation of said supervisory means and to the transmission of a start signal from said timing signal producing means for rendering said seizure responsive means inoperative with respect to said holding circuit and for thereupon causing said holding circuit to be completed over a different path, means operative in response to the operation of said relay to its second position and to the subsequent transmis sion of a rst signal from said timing signal producing means for releasing said relay to its normal position and there-after operative in response to the release of said relay for causing said holding means to be operated by a second signal transmitted from said signal generating means, means operative in response to the release of said relay and to the subsequent transmission of a third signal from said timing signal producing means for operating said relay to its rst position, a tone source, and means operative in response to the operation of said relay to its irst position for connecting said tone source to said connection.

4. The system set forth in claim 3 and having in addition means operative in response to the establishment of a connection through said switch train over a particular route for operating said relay to its second position and for thereafter maintaining said relay operated in its second positoin, whereby the release of said holding means by said timing means is prevented.

References Cited in the tile of this patent UNITED STATES PATENTS 2,291,496 Newstedt July 28, 1942 2,595,388 Kessler May 6, 1952 2,647,163 Lomax July 28, 1953 2,702,314 Pharis Feb. 15, 1955 

